South Wales Caves: Cave Sites

Porth yr Ogof Main Entrance from inside

Porth yr Ogof

Porth Yr Ogof cave is in the Brecon Beacons National Park, South Wales, UK. The nearest village is Ystradfellte which is about 1 KM to the north. Both the village and the cave lie on the River Mellte, which is Welsh for ‘Lightening’ – attributed due to the speed at which the river levels rise and fall in wet weather.

The name Porth Yr Ogof translates best as ‘Gateway to the Cave’ in Welsh.
It boasts the largest cave entrance in Wales which is the main entrance at 17.5m wide and 5m high. There are 14 other known entrances to the cave.

The river Mellte can be seen to enter the Main Entrance (entrance ‘E’ on the survey) and can be followed right the way through the cave in dry weather to re-emerge at the Resurgence (entrance ‘N’ on the survey).

Survey by University of Bristol Speleological Society (UBSS) and the Cave Diving Group

The first recorded explorations of the cave were in the 18th century by travellers. The cave was fully explored and surveyed by various caving organisations from 1936 onwards.

In the 1950s there were studies conducted into the flora and fauna of the cave.

The Ystradfellte reservoir lies at the head of the valley and the river Mellte flows down through Ystradfellte village, where it sinks underground at Church Sinks. It re-appears some 900m (in a straight line) downstream at Porth yr Ogof cave. A dye connection made in 1964 recorded a time of 2.25 hours to re-appear at Tradesmans entrance (Entrance ‘C’ on the survey).

Cave diving began in Porth yr Ogof in 1961 and the Cave Diving Group have been occupied with explorations ever since.

References:

Lloyd O.C, Standing P.A, Newton M.D. Porth Yr Ogof, Powys. Reprinted from proceedings of the University of Bristol Speleological Society, Vol. 12, No 2, 1970 and vol. 15, No. 3, 1980

Little Neath River Cave

Little Neath River Cave (known as LNRC) is in the Nedd Fechan Valley, Breconshire, South Wales, Uk. The cave was discovered in 1967 by the University of Bristol Speleological Society (UBSS) by diving the flooded cave passage (sump) which connects the cave to another adjacent cave called Bridge Cave.

The cave is on the East bank of the Nedd Fechan river and is on private land. Permission from Blaen Nedd Isaf farm and an access fee are required prior to entering the cave.

The entire system is 8,800m long and the entrance floods to the roof. It should only be accessed in the driest, most stable of weather.

The system has no less than 8 sumps (the detailed description of LNRC in the UBSS proceedings is out of date and sump 8 has now been discovered and dived) and passing sump 4 allows the diver to access very grand and well decorated dry passage called the ‘New World’.

Project Baseline South Wales is primarily concerned with sump 1, between the adjacent Bridge Cave and LNRC. Albino trout are known to reside here and there is the occasional pollution issue in LNRC. The project aims to monitor the health of this sump and the cave passage leading to it and the fauna that reside there.